Estimated Grass Grazing Removal Rate in a Semiarid Eurasian Steppe Watershed as Influenced by Climate

Abstract

Grazing removal rate of grasses needs to be determined for various climate conditions to address eco-environmental concerns (e.g., desertification) related to steppe grassland degradation. The conventional approach, which requires survey data on animal species and heads as well as grass consumption per individual animal, is too costly and time-consuming to be applied at a watershed scale. The objective of this study was to present a new approach that can be used to estimate grazing removal rate with no requirement of animal-related data. The application of this new approach was demonstrated in a Eurasian semiarid typical-steppe watershed for an analysis period of 2000 to 2010. The results indicate that the removal rate tended to become larger, but its temporal variation tended to become smaller, from the upstream to downstream. Averaged across the watershed, the removal rate ranged from 63.9 to 401.0 g DM m´2 (or 22.4 to 60.9%) during the analysis period. As expected, the removal rate in an atmospherically wetter year was higher than that in an atmospherically drier year. Nevertheless, none of the eleven analysis years had a removal rate higher than the threshold value of 65%, above which the risk of grassland degradation would become much greater.

Water–Soil–Vegetation Dynamic Interactions in Changing Climate

“…The new algorithms presented in four articles [39,40,44,45,48] provide necessary tools for better modeling effects of grazing on steppe grassland degradation, future climates on sedimentation at watershed scale, micro-topographic features (e.g., puddles) on hydrologic processes, and infiltration on the translational stability of long slopes. In addition, two articles [41,43] found that human activities were the primary reason for runoff reduction, whereas, another article [42] showed that climate variability was the dominant driver for decreasing trend of streamflow.…”

“…The articles cover a wide range of geographic regions across China [39][40][41][42][43][44]46,47,49,50] and the United States of America (USA) [45,48] with contrasting hydro-climate, soil, and vegetation conditions. Thus, the results presented in these articles can have global inferences: the data, analysis/modeling approaches, results, and findings will lay a solid foundation to further our scientific understanding of water-soil-vegetation interactions, ultimately leading to the development of practically effective solutions to sustaining the globe's ecosystem health and productivity.…”

“…Wang et al [40] proposed a new method that utilized remote sensing images and a total Net Primary Production (NPP) model to predict grazing removal rate of grasses under different climate conditions at a watershed scale. The authors applied their method to evaluate the potential risk of steppe grassland degradation in a semiarid watershed in the Eurasian Steppe, demonstrating the advantages of the new method over the conventional approach that is over reliant upon detailed animal survey data.…”

“…The specific topics include steppe vegetation affected by climate change [39,40], interactions of climate, anthropogenic activities, and watershed hydrology [41][42][43], SWAT modeling for quantifying topography-controlled hydrologic processes and sediment yield [44,45], snow cover and frozen soil dynamics in cold regions [46], quantification of plant transpiration in arid/semiarid environment [47], coupled infiltration-runoff modeling for slope stability analysis [48], and assessment of nutrients in aquatic systems [49,50]. In terms of methodologies, these studies involve both field/laboratory experiments and mathematical modeling across different scales.…”

“…Over 40% of the globe's grasslands have been somewhat altered from their indigenous state, including more than 70% of the Inner Mongolian steppe grasslands of China [17], which are part of the Earth's largest and most characteristic grassland ecosystem, the Eurasian Steppe (or Great Steppe). Here, degradation has caused serious environmental and ecological problems including more frequent and damaging hydrologic extremes (i.e., flooding and/or drought), desertification, dust storms, which has led to shortage of agricultural commodities [9,10,18]. These problems are in turn likely to threaten the sustainability of "grassland agriculture," a system of agriculture in which the major emphasis is on grasses, legumes, and other fodder or soil-building crops [19].…”